More than 700 Korean tourists are believed to be stranded in Bali because of ash from the island's Mount Agung volcano eruption.

The Ministry of Foreign Affairs said Tuesday that it has yet to figure out the exact umber of stranded Korean tourists, but according to industry officials, 700 to 800 Koreans are presumed to be stuck there after Tuesday's return flight was canceled.

The island's Ngurah Rai International Airport will be shut until 7 a.m. today, according to Sutopo Purwo Nugroho, spokesman for Indonesia's National Disaster Mitigation Agency.But scientists say Agung's volcanic activity may intensify over the coming days. That means nearly 60,000 travelers from around the world might have to wait longer.Agung's last major eruption occurred in 1963 and killed about 1,100 people.Bali is one of the most popular destinations for Koreans. According to travel agencies, about 16,000 Koreans visit the island every month. But following the eruption, hundreds of people have canceled their planned trips.